# Thermodynamic Jargon

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```					                                         Thermodynamic Jargon

Open System : mass flows into or out of the system, across the system boundary

Closed System : no mass crosses the system boundary

Isolated System : the system does not interact with the surroundings, i.e., no mass crosses the
system boundary, no heat crosses the system boundary, the system does no
work on the surroundings, and the surroundings do no work on the system

Cycle : When the thermodynamic state of a substance, e.g. (T , P) or (T or P , x), is changed in
several processes or paths but the substance is finally returned to it’s original
thermodynamic state, that substance is said to have undergone a cycle; the changes
in the thermodynamic state may occur in either a closed or open system, i.e., the
changes may occur in a system with no mass crossing the system boundary or in one
which includes a fluid flowing through several processes but finally returning to the entry
of the first process in the sequence.

AS : Surface Area perpendicular to the direction of heat transfer

AX : Cross Sectional Area perpendicular to the direction of the mass flow of a stream ;
e.g., AX,1 for stream 1

CP (T, P) : Heat Capacity of a substance ; i.e., the thermal energy, in the form of heat absorbed
at constant pressure per unit mass or mole of a substance, associated with a one
degree increase in temperature ; e.g., CP, NH3 = the heat capacity of ammonia

C 0 ( T only) : Heat Capacity of an Ideal Gas ; i.e., the thermal energy, in the form of heat
P
absorbed at constant pressure per unit mass or mole of a substance, associated
with a one degree increase in temperature ;
e.g., C 0      ( T only) = the ideal gas heat capacity of air
P, air

CV (T, v) : Heat Capacity of a substance ; i.e., the thermal energy, in the form of heat absorbed
at constant volume per unit mass or mole of a substance, associated with a one
degree increase in temperature ; e.g., CV, NH3 = the heat capacity of ammonia

C 0 ( T only) : Heat Capacity of an Ideal Gas ; i.e., the thermal energy, in the form of heat
V
absorbed at constant volume per unit mass or mole of a substance, associated with
a one degree increase in temperature ;
e.g., C 0      ( T only) = the ideal gas heat capacity of air
V , air

F1 : Mass Flow Rate of stream 1

F : Force (scalar) ; e.g., Ffriction is equal to S

g : Gravitational Acceleration (scalar) : local acceleration of gravity [ m s 2 or ft s 2 ]

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h : mass or molar specific enthalpy of a substance (see specific volume for nomenclature)

P : Pressure (scalar) of a liquid, gas, or solid substance ; e.g., Patm = atmospheric pressure,
P1 = pressure of stream 1

PC :     Critical Pressure (scalar) of a substance ; e.g., PC,NH3 = critical pressure of ammonia


Q : Power or Rate of Energy Transfer Associated with Heat Transfer, also Rate of Heat

Transfer [kW} ; + if transferred to the system ,  Q  Q dt and Q   Q
Q : Heat or Energy Transferred to or from the System [kJ} ;   + if transferred to the system ,

 Q  Q dt and Q   Q  

Q     : Power or Rate of Energy Transfer Associated with Heat Transfer per unit surface area
USA
perpendicular to the direction of heat transfer, also Rate of Heat Transfer [kW} ; + if
 
transferred to the system ,  Q  Q       dA and Q    Q
      
USA S

R : Universal Gas Constant in P v = Z R T for example

s : mass or molar specific entropy of a substance (see specific volume for nomenclature)

TC :     Critical Temperature of a substance ; e.g., TC,NH3 = critical temperature of ammonia

T : Temperature of a substance ; e.g., T0 = ambient temperature,
T1 = the temperature of stream 1 (or R for all thermodynamic equations

u : mass or molar specific internal energy of a substance (see specific volume for nomenclature)

vC : Critical mass or molar specific Volume of a of a substance ; e.g., vC,NH3 = critical specific
volume of ammonia

vG : Velocity of the Center of Mass of the System : e.g., vG,gas

vL (T , P) : mass or molar specific volume of a Subcooled or Compressed Liquid ; in the liquid
region of the P-v or P-T diagram

vSL (T or P) : mass or molar specific volume of a Saturated Liquid : on the line associated with
the ‘the ‘saturated liquid-vapor dome’, exists in equilibrium with a single, ‘minute
drop’ of vapor

vV (T or P) : mass or molar specific volume of a Vapor : on the line associated with the ‘saturated
liquid-vapor dome’ of the P-v or P-T diagram, exists in equilibrium with a single,
‘minute drop’ of saturated liquid)

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v (T , P) : mass or molar specific volume of a Gas ; in the gas region of the P-v or P-T diagram
avg
v       (1-x) vSL (T or P) + x vV (T or P) : average value for the mass or molar specific volume of
a Mixture of a Saturated Liquid and a Vapor :
m
vapor
where     x 
m         m
vapor       saturated liquid

Related Nomenclature : v (T , P)            vL (T , P)
vf (T or P)    vSL (T or P)
vg (T or P)     vV (T or P)
v  (1-x) vf + x vg

vavg : Average Velocity of a Fluid Flowing in a Conduit or Pipe :
v2
avg,1
e.g., in (F1 P vavg,1) or        for stream 1
2
KE

W : Power or Rate of Energy Transfer Associated with Work, also Rate of Work Transfer [kW}
; + if transferred to the system ,  W  W dt and W    W


W : Work or Energy Transferred to or from the System [kJ} ;     + if transferred to the system ,
 W  W dt and W    W


Z ( T , P ) : General Compressibility Factor in P v = Z R T

ZC: : Critical Compressibility Factor of a substance ; e.g., ZC,NH3 = critical compressibility
factor for ammonia

z : Height above some arbitrary datum or relative to a specified coordinate

KE : Velocity Profile Average Factor for the Kinetic Energy of a flowing stream ;
e.g., KE = 1.0 for turbulent flow, KE = 0.5 for laminar flow

M : Velocity Profile Average Factor for the Linear Momentum of a flowing stream ;
e.g., M = ?.? for turbulent flow, M = ?.? for laminar flow

:      Volume Expansivity of a Liquid ; e.g.,

:      Isothermal Compressibility of a Liquid ; e.g.,

x , y : scalar coordinates

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